Design and Control of a Novel Compact Nonlinear Rotary Magnetic SEA (MSEA) for Practical Robotic Gripper Implementation

In this letter we present a novel design of a nonlinear series elastic actuator based on magnetic repulsive forces. The primary application of the actuator is for simple robotic grippers that operate in close proximity to the environment and are exposed to hazards of collision frequently. The design of the rotary magnetic spring proposes a unique configuration that maximizes the torque profile range while minimizing size and weight, which makes it practically implantable in robotic gripper applications. The torque profile of the proposed configuration was verified with FEM simulations and a series of experiments. The proposed SEA (MSEA) was controlled with a gain scheduling method which adjusts the gains of a PID controller based on the estimated stiffness of the spring in real-time. MSEA performance characteristics to accurately track torque and absorb shocks were evaluated and verified through a series of experiments.